Rotary switch



July 7, 1959 G. H. SCHACHT 2,394,096

ROTARY SWITCH Filed June 25, 1957 4 Sheets-Sheet 1 ll H INVENTOR.GUNTERI H. SCHACHT ATTY.

July 7, 1959 s. H. SCHACHT ROTARY SWITCH 4 Sheets-Sheet 2 Filed June 25,1957 L Ifllavl'l... I I l I] I i I I ll BWANW WU INVENTOR. )f" GUNTER H.SC CHT ATTY.

July 7, 1959 Filed June 25, 19s? G. H. SCHACHT ROTARY SWITCH FIG. 7

' 4 Sheets-Sheet 5 INVENTOR.

GUNTER H. SC ACHT 'YfQ I ATTY.

July 7, 1959 G. H. SCHACHT 2,894,096

ROTARY SWITCH Filed June 25, 1957 4 Sheets-Sheet 4 F l G 9 FIG. 13

IIIIIHIII lll lllll 55 fi====== 63 f:

.5 H H 65 5 H 2 52o 52w 52 52X FIG I IG. IO 52 INVENTOR.

GUNTER H. SCHACHT BY 6 a) ATTY.

United States Patent ROTARY SWITCH Gunter H. S'chacht, Vestal, N.Y.,assignor to General Telephone Laboratories, Incorporated, Chicago, 111.,a corporation of Delaware Application June 25, 1957, Serial No. 667,933

12 Claims. (Cl. 200-105) 1 The present invention includes many of thefeatures shownin such patents as 2,522,715 and 2,710,896 both issued toK. W. Graybill, et al. dated respectively September 19, 1950 and June14, 1955. These patents show the general construction of a rotary switchand its mechanisms; however the present application, of course, has manyfeatures not included in these patents which features will be'pointedout and amplified.

'A major object of the present invention is to provide a switch havingits driving pawl and holding detent each formed from a length of musicwire into U-shaped element.

Another object of theinvention is to provide a ratchet wheel to becontacted by these U-shaped elements, which wheel is molded or machinedfrom fabric base phenol, linen bakelite or nylon material. Further,between each of the teeth of the wheel is formed separated by a U-grooveto firmly nest the music wire elements.

A further'object consists in the use of hook shaped metallic wiper armsmolded as part of the wiper assembly.

To each of these arms may be attached demountable individual wiper tipswhich can be firmly locked into place and yet be readily removed ifrequired.

- Another object resides in the use of an armature bearing pin ofsimple, loose tolerance construction. This is accomplished by weldingthe bearing pin directly to the armature and providing a pie-stressedleaf spring or shim as one of the surfaces in contact with the bearingpin. Thus the only surface of the hearing which will be subject to wearis the surface of contact with the holding bracket or yoke.

A major feature of the invention consists-of the use of a solidsemi-circular conductingring bonded to each bank level insulator.Through the use of twin contactors on the wiper tip, one of whichcontacts the ring and the other the successive terminals of the level, a

circuit is completed from the terminals to the ring con-.-

The usual wiper brush arrangement for :com-

ductor. pleting the series circuit is therefore unnecessary.

Another feature of the invention consists of forming a seriesequally-spaced, raised elliptical prisms on each level insulator duringthe insulator for blanking operation. The raised prisms serve as a meansforpositioningthe terminals of the level in assembly. In operation, theprisms serve as a means for maintaining a level path of travel for thewiper tips across the normal valleys between the contacts. I

These features, objects and many others will become apparent whenreviewing the drawings. Fig. 1 shows a side view of the switch asassembled and Fig. 2 shows a top view. Fig. 3 shows thedriving mechanismof the switch while Figs. 4, 5 and 6 show in more detail some of theelements in the construction of the armature assembly of the drivingmechanism. Fig. 7 shows a representative bank level with some of thecontacts shown in detail so that the construction of a bank level may bemore clearly understood. Figs. 7a and 7b show in detail the section of atypical contact. Fig. 8 shows a typical bank spacer or insulator. Fig. 9shows generally the construction of a wiper assembly. Fig. 10 shows inmore detail the wiper to bank contact relationship. Fig. 11 shows awiper arm and Fig. 12 a wiper tip in position for mounting to the wiperarm of Fig. 11. Fig. 13 shows an end view of the wiper of Fig. 12.

In more detail the switch will be analyzed by component units as.follows: first, the driving mechanism; second, the driven mechanism(wiper assembly) and third, the stationary or bank assembly. Theoperation of the switch will complete the description.

Driving mechanism The driving mechanism generally consists of a motormagnet and armature assembly. As shown in Figs. 1, 2 and 3, theoperating coil 33 is provided with an inverted U-shaped coil core 32.One leg of the U extends through the center of the coil and the otherleg serves as a heelpiece. By the use of this type of core, the numberof air gaps-in the magnetic circuit is reduced and a more eflicientmagnetic path is produced.

The armature assembly is indirectly pivoted to the heelpiece leg of core32. This pivoting is accomplished by the use of yoke 35 which is mountedto core 32 by using standard round head screws. At its lower end theyoke has an open semi-circular section to retain the armature bearingpin- 36 in place. Bearing pin 36, which is shown in more detail in Fig.4, is spotwelded to the projections of armature bracket'34- To completethis end of the assembly a shim or leaf spring 37 is mounted between thecore 32 and bearingpin 36. This spring is pre-stressed so that itmaintains pressure against bearing pin 36. The shim is mounted under thescrews which retain yoke 35 to the heelpiece leg of core 32 andmaintains bearing pin 36 away from-contact with the core leg 32. 1Armature bracket 34 is of a magnetic material so that it will be drawninto contact with the coil leg of core 32 on energization' of the coil33. This energized position is the one shown in Fig. 3.

Attached to the armature bracket 'by screws .44 is I the armature,extension 31 which will be called the arma ture hereinafter. The.armature is a channel shaped length of aluminum or other light weightmaterial. The channel shape and the light weight material are combinedto produce an armature having a low mass for the length necessary. Alongthe'length ofthe armature toward its free-end is mounted pawl bracket38. Held, in placeagainst this bracket 38 by holder 39 andleaf-springl42 is the driving pawl 40. This pawl is mounted astraddlethearmature as shown in Fig. 5. This pawl 40-is made of a single length ofmusic wire formed into the shape shown. By using -music. wire, three ormore effects are achieved. First, the pawl can be mounted in a simplearrangement as shownin Figs. 3, 5, and 6 and no bearings.

, are necessary. ;Second, since the music wire isia high ping pawl 41whose transverse width, is aboutequal to,

gradespring steel, it isrigid yet has inherentspring serves a secondarypurpose by serving as the actuator for interrupter springs 43 which maybe provided as required.

At the outermost tip of armature 31 is secured stopthe width of armature31. By this construction th e s'tOp ping pawl has enough width to engagethe entire face of a tooth on the ratchet wheel and thus minimize wearon the teeth. A backing rod 45 which has tapped holes to accommodateholding screws 46, one of which is shown in Fig. 3, is mounted throughthe channel armature substantially as shown, to hold stop pawl 41.

In viewing Fig. 2, it can be seen that the center-line 47 of coil 33 andcore 32 coincides with the center of action of the armature, its drivingpawl, the hold detent, and the effective center of the contacting teeth.By this construction a direct straight line linkage is used which allowsa maximum of the developed energy to be trans mitted into effectivework.

Driven mechanism The driven mechanism or wiper assembly contains theratchet wheel, the rotary shaft, the wiper block carrying the wiper armsand the wiper tips. These elements are shown in Figs. 1, 2, 3, 9, 10,11, 12 and 13. The ratchet wheel 54 consists of a circular disc ofnylon, linen or other fabric base phenolic material. Along its peripheryare formed by machining or molding 102 equally spaced teeth 56, 56a,etc. having the shape shown in Fig. 3. The shape shown includes arearward- 1y sloped leading face and a radial trailing face on eachtooth. Between successive teeth are U grooves having a sufiicently largecircular section to fully nest driving pawl 40.

At the center of the wheel 54 is a shaft 55 about which the wheel isdriven (shown in Fig. 9). The shaft 55 has the wheel end threaded andhas a spacing ring nut 61 placed inward of the threaded portion. At theopposite end of shaft 55 is a recessed slot outward of which the shafthas a smaller diameter faced surface.

The wiper block 51 is a molded rectangular solid through the center ofwhich has been molded bushing 58 of suitable bearing material. Thebushing has a series of circumferential oil grooves on its inner surfaceto circulate the shaft lubricant. A pair of studs 59 are also moldedinto the block. These studs have radial holes tapped in their side toreceive screws 64 which are used to mount ratchet wheel 54 and metallicspacer 60 to the wiper block. Shaft 55 protrudes through the far end ofwiper block 51 and retaining ring 57 slides into the shaft recesslocking the shaft in position to the wiper block.

Also molded into block 51 are extension wiper arms 52 a, b j and k.These arms are aligned in pairs along the length of the block. Thesearms are embedded such that emboss 65 as shown in Fig. 11 is facingrearward in the direction of rotation of the ratchet wheel. An identicalsecond set of wiper arms 52 m, n y and z protrude from the opposite endof the block. These also have embosses 65 facing rearward in thedirection of rotation. Each of these extension arms is insulated fromall the remaining arms on the block by means of the material in theblock proper. In the present embodiment sixteen levels can beaccommodated. With minor revisions more or less wiper levels couldnaturally be provided.

Referring to Figs. 11 and 12 can be seen a representative extension arm52 and wiper tip 53. Emboss 65 on arm 52 is faced rearwardly in thedirection of rotation of the ratchet wheel. Arm 52 has a hook shapewhich can readily be squeezed by pressure on boss 65. The wiper tip 53has a notch 66 which is of proper size to retain boss 65. The wiper tipis slid onto the extension arm until boss 65 catches in notch 66 to lockthe tip onto the arm. The outer end of the wiper tip has a pair ofbifurcated contactors 67 and 68 which are pre-tensioned to theapproximate shape shown in Fig. 13. These wiper tips may be detachedindividually by squeezing boss 65 on arm 52, toward the back surface ofthe arm and the wiper tip may be slid off the arm.

-As can be seen in Fig. wiper tips are of two basic shown as 53a andthat shown as 53b. The

difference between these is simply that one, 53a, is made for contact onits left side and the other, 53b, for contact on its right side. Withthis exception, the wipers are otherwise identical.

As shown in Fig. 2, each wiper arm contains a wiper tip. This assemblyis used for 16 levels of 50 points each. For eight levels, pointsoperation, alternate wiper tips on each end of the wiper assembly areremoved. An example of this would be to remove alternate Wiper tips suchas 53a, 53n 53 53z. With the replaceable wiper tips of the presentinvention the switch could be changed from 50 point to 100 pointoperation by removal of the wiper tips as exemplified above, or in thereverse direction from 100 point to 50 point by the addition of thesewiper tips and proper wiring of the bank to agree.

Stationary assembly The stationary assembly consists of the contact banklevels of the switch and the stationary frame mechanism The bankassembly is composed of a number of pairs of levels of arcuate rows ofbank contacts. Each pair of levels may be considered as including aright hand level and a substantially identical left hand level. Eachlevel consists of a number of contacts equi-angularly spaced, as shownin a representative manner in Fig. 7. The general shape of the contactsmay be seen in this figure also. A contact such as 94b consists of aninner contacting portion, a holding body having holes 98 and the outerterminal leg. The holes 98 along circumferential band it of Fig. 7 areholes which are pierced to form a ragged shoulder or edge as is shown inFig. 7b. The contacts are placed in the proper alignment on an insulator95 which extends past the contacting portion of the contacts. Thecontacts are then squeezed onto the insulator, the ragged edge firmlyembedding the contacts into the insulator.

In Fig. 7 may also be seen elliptical prisms which are formed into thestructure of the insulator when the insulator is being blanked. Theseprisms have a height slightly lower than the height of a contact. Thecontacts in assembly are placed between the prisms. The minor diameterof the ellipse is substantially the proper between-contact distance sothat when the contacts are placed on the insulator, they areautomatically spaced evenly.

A secondary purpose of these elliptical prisms is to provide a raisedsection between successive contacts in the path of travel of a wiper.Thus the valleys between contacts are eliminated and a level path oftravel of the wiper tips across the contacts is insured. In this way theconstant flexing and stressing of the wiper tips across contacts isrelieved, adding to the life expectancy of the wiper tips Each levelinsulator has bonded thereto a semi-circular conducting ring 97 whoseinner circumference is coplanar with the inner circumference of theinsulator. This feature may be seen more readily in Fig. 10. Thisconducting ring terminates in terminal leg 94x at its upper rightextremity. For this reason the level of Fig. 7 would be considered aright hand level. A left hand level would be identical to this with thesingle exception that a left handed level would have its conducting ringterminating leg at the upper left hand extremity of the level.

To explain a switch bank, it should prove easier to assume a switchbeing built vertically'with a final result as shown in Fig. 2. To start,end frame 92 is placed in the position shown in Fig. 2 with the screws87 shown in Fig. l placed in the holes. then placed on the frame withscrews 87 extending through the spacer holes 104. Next a left handedlevel would be placed on the screws 87 with the contacts down so thatthe conducting ring terminal is at the left side of the assembly. Next aright handed level is placed with its contacts up. A spacer 96follows,'then another lefthatidi Insulator or spacer 96 'is level, aright hand level, a spacer, etc. until the required number of levelshave been included.

Fig. shows a section B from Fig. 2. This section shows in cross sectionthe first regular contact in the bank. Shown in the drawing are a lowerspacer 96g, a right hand level including contact 94g, insulator 95g andconductor ring 97g. Above this is a left hand level includ ing insulator95 contact 94 and conducting ring 97f with spacer 96f and steel bracket99 atop the assembly. Bracket 99 is essentially the same shape as spacer96; however the holes, corresponding to 104 on spacer 96 are tapped insteel bracket 99 to receive screws 87. The bank assembly is thentightened and squeezed to comprise a unit having its outer surfacessteel bracket 99 and end frame 92.

To mount the bank to the switch, a spacer 101 is used to space the banka suflicient distance from outer frame 91 and keep the bank frominterference with ratchet wheel 54. The bracket 91 serves as the sideframe of the switch at the coil side and is mounted to the bank by meansof a series of screws received in tapped holes on steel bracket 99. Bythe removal of these screws, the bank assembly may be dismounted fromthe switch frame without disturbing the alignment of the coil side frame91 and the remaining switch elements.

Stationary frame assembly The stationary frame 81 consists of themounting to which the coil core and the remainder of the switch elementsare mounted. Reinforcing brackets may be added wherever needed tofurther support the armature assem bly and maintain the proper relativeposition of the integral units of the switch. The use of a reinforcementsuch as mentioned would not add patentably to the features shownhowever. As shown, the stationary frame 81 has mounted to it aninterrupter spring pileup 43, operative on movement of the armature asreflected through bracket 38. The frame further contains the backstopand adjusting screw 82 for driving spring 84. Spring 84 is afrusto-conical coil spring of the type frequently used in indirect driveswitches as the main operating spring. An arm 85 is provided on thestationary frame for mounting the hold detent spring 86. This detent ordog is made up of a U-shaped length of music wire of somewhat lesserdiameter of the driving pawl 40 but having the same basic shape.

Operation As in the operation of any electromagnetic switch, a pair ofdirect current leads must be provided for the coil. Means forinterrupting the direct current must also be provided and these meanscan be the interrupter springs 43 of the switch.

When the current is applied to the coil 33, armature bracket 34 which isof magnetic material is drawn up against coil core 32 to complete themagnetic circuit. Armature 31 is thereby drawn up compressing spring 84.Stopping tooth 41 is drawn out of contact with ratchet wheel 54 anddriving pawl 40 is lifted out of contact with the tooth with which ithas been engaged. Pawl 40 is pre-stressed toward the ratchet teeth sothat on energization of the motor magnet, the pawl drops into the groovebehind the previously engaged tooth.

It should be noted that the gear teeth of ratchet 56a, etc. have asloped leading edge so that the pawl 40 may slide out of engagementsmoothly. Further the groove diameter between the teeth is roughlycomparable to the pawl diameter so that the pawl nests comfortably atthe base of the groove. Hold detent 86 maintains the ratchet wheel atrest by holding the tooth with which it has been in contact. This is thecondition of the switch in Figs. 1 and 3.

When the armature is drawn up, the pawl bracket 38 causes the spring ofpile up 43 to break, opening the circuit to coil 33 (assumingself-interrupted operation).

The armature is released due to spring 84 discharging its compressedforce. Pawl 40 is forced against the radial trailing edge of tooth 56and pushes the ratchet wheel forward. When a finite angle of revolutionhas passed, stopping tooth 41 mates with the tooth adjacent its priorposition, stopping the motion of the ratchet wheel. The relationshipbetween the driving surface (the base of the U of the pawl 40 and thetip of stopping tooth 41 is such that one tooth and only one tooth ispassed before stopping tooth 41 is engaged with ratchet Wheel 54. Holddetent is slid out of its contact during this movement of the wheel andfalls into the next groove.

A circuit is then completed between ring conductor such as terminal 94x,ring conductor 97, wiper tip ground arm 67, wiper tip 53, contact arm 68to the contact such as 94m as shown in Fig. 1. Successive steps are madein the same manner to traverse the bank contacts sequentially.

What is claimed is:

1. In an indirect drive rotary stepping switch, a rotatable wiperassembly and driving means for rotating said wiper assembly, saiddriving means including an energizable electromagnet, an armatureactuated in response to energization of said electromagnet, a drivingpawl secured astraddle said armature, said driving pawl comprising aU-shaped length of longitudinally stifi, transversely flexible musicwire, said rotatable wiper assembly including a ratchet wheel having aplurality of teeth spaced equally around its periphery, the base of saidU-shaped driving pawl being impelled against one of said teeth ondeenergization of said electromagnet to cause said ratchet wheel torotate, means for holding said ratchet wheel stationary betweenimpellations of said driving pawl, said holding means comprising aU-shaped length of music Wire disposed to contact said wheel betweensaid teeth, means coupled to said driving pawl for stopping said ratchetwheel after said wheel has rotated through a predetermined acute angle,said coupled means comprising a rigid tooth, said driving pawlcompensatorily flexible for misadjustments in said tooth-to-pawldistance when said ratchet wheel is stopped by said rigid tooth.

2. In a rotary stepping switch having a frame, a plurality of contactsaifixed to said frame, said contacts arrayed in a plurality of arcuatetiers, each of said contacts having an individual external terminal,each of said tiers having an equally spaced, identical plurality of saidcontacts, each of said tiers having associated therewith a solid arcuatesector of a conducting ring, a rotatable wiper assembly axially mountedto said frame, said wiper assembly having a plurality of pairs ofopposed contacting arms, each one of said contacting pairs of arms beingadjacent a different one of said tiers, each of said arms detachablybearing a pair of conductively connected wiper tips, one of said pair oftips capable of conductively contacting the contacts in the saidadjacent tier, the other of said pair of tips capable of contacting saidconducting ring, a terminal connected to said conducting ring, drivingmeans for rotating said wiper arms in a series of steps, each of saidsteps comprising a finite sector of a circle, said sector ofcircumferential are equal to the spacing between the contacts in a tier,said one wiper tip consecutively contacting the contacts adjacent saidwiper arm on said steps, said other wiper tip on contacting said ringsector completing from said conducting ring sector terminal, throughsaid conducting ring sector, said other wiper tip, said one wiper tip toconsecutive contacts and their external terminals.

3. In a rotary switch having a frame with a plurality of arcuate rows ofequally spaced terminals secured to said frame, means axially linked tosaid frame for rotating in a series of finite steps to traverse saidterminals, said axial means comprising a base unit, a plurality of hookshaped arms parallelly aligned in said base, each of said armsindividually adjacent one of said rows of terminals, each of said armshaving a shoulder outwardly embossed at'the tipofsaid hook'shaped arm,individual contacting means removably mounted in a slidable manner toeach of said'arms, each of said contacting means having a notch thereinfor encircling said shoulder thereby cooperatively locking saidcontacting-means to said arm, each of said contacting means disposed toconductively contact consecutively the individual terminals in a rowduring saidseries of finite steps.

4. In a rotary stepping switch, an electromagnet, an armature ofmagnetic material and a wiper assembly, said electromagnet comprisingaU-shaped coil core and a coil disposed around one leg of the -U-shapedcore, means pivotably securing saidarmature to'the other leg of saidU-shaped core, said pivotable means comprising a cylindrical ax-lewelded to saidarmature-and a bracket secured to said other leg forholding said axle, said bracket restrictingsaid axle to'rotati-vemotion, said axle restrained to rotation through a predetermined arc, achannel shaped member mounted cooperatively with said armature, saidwiper assembly comprising a rotatively mounted ratchet wheel havingaplurality of teeth equally spaced along its periphery, pawls aifixed tothe channel member for engagement with the teeth of said ratchet wheel,saidelectromagnet energizable to attract said armature against said oneleg of the coil core, said channel member'controlled by said'pivotingtodraw said pawls out'of engagementwith the teeth of said ratchet wheel,spring means compressed by the energization of said magnet and restoredresponsive to the deenergization of said electromagnet for driving saidpawls into contact withsaid ratchet thereby causing said-wiperassembly'to rotate through a predetermined angle of revolution.

5. In a rotary switch, a stationary frame having a semi-circularterminal bank mounted thereto, said bank comprising a plurality ofpairs'of levels,-each level including an inner arcuate conducting bandand an outer band having a plurality of equi-angularly spaced contacts,means for insulating each of said contacts from the remaining contactsand from the conducting bands, each of said levels having enantiomorphicrelation to the next adjoining levels, means for simultaneouslyconnecting a contact in each level and the conducting ring of the samelevel, said connecting means comprising an individual wiper for each ofsaid levels, each of said wipers individually detachably mounted to arotatable member,

each of said wipers sequentially contacting the contacts.

ofzsaid level on rotation of said rotatable member.

6. In a rotary stepping switch, a motorrnagnet having an energizableelectromagnetic coil integral thereto, an armature pivotably mounted tosaid motor magnet, a rotatable ratchet wheel having a plurality ofteeth,,said armature having means for tactually engaging teeth of saidratchet wheel, said engaging means slidably moved across a tooth of saidwheel on energization of said-coil, said engaging meanstimpellablyforced against a tooth of said wheel on deenergization of said core tocause said wheel to rotate through a' predetermined are, said motormagneticoilhaving a plane through its centerline at which planethemagnetic effect of said coil is a maximum, said armature having itscenterlinecoplanar with said centerline plane, said engaging meanshaving a centerplane of action incommon with the center plane ofactionof said teeth, said center planes and center lines coplanar with thecenter plane of saidelectromagneticcoil.

'7. In a rotary stepping switchcomprising a stationary frame, a motormagnet and a rotating wiper assembly, an armature pivotably mounted tosaid magnet, means forzrotating said wiper assembly in a step-by-stcpman ner, said rotating means comprising a driving pawl secured to saidarmature and a ratchet wheel having a plurality of teeth, said drivingpawl comprising a U-shaped length of music wire, grooves between theteeth of said ratchet for receivingsaid driving: pawl, each of saidgrooves having a substantially circular bottom fornesting said drivingpawl, holding means mounted to said frame, said holding-means comprisinga U-shaped* length of music Wire, the wire of said-holding meansbeingmeans thereafter slidable across-:the teeth of said wheel,

further means afiixed to said armature and having a predeterminedspatial relation to said driving pawl'for stopping the rotation of saidratchet-wheel after a predetermined arc of revolutionhasbeen completed,said holding means thereaftennesting in a round groove of said ratchetwheel and holding said wheel stationary.

8. In a rotary stepping switch, adriving means for producingreciprocating motion, rotatable 'meansdriven by said reciprocating meansand a stationary assembly holding both saidprior mentioned means,saidreciprocating motion impartedtoa driving pawlintegraltosaid drivingmeans, said driving pawl comprising a prestressed fU formed length ofsteel wire, said pawlsequentially contacting the respective teeth of aratchet wheel to:rotate said wheelthrough a predetermined arc on'each.of saidreciprocating cycles, said rotatable means including said ratchetwheel and-a wiper block coupled thereto to rotate in conjunction withsaid wheel, .said stationary assembly having a .U formed lengthofsteelwire for holding said wheel stationary between said arerotations, said wiper block havingia first plurality of arms protrudingtherefrom in aligned array, a second pluralityof arms aligned oppositesaid firstplurality of arms, each of said arms electrically insulatedfromithe remaining of said arms, each of said'arms having asubstantially recurved extremity and a shoulder at the tip of saidrecurve, individual bifurcated contacting means each having a sleevesection 'for detachably mounting to the recurved extremity of one ofsaidarms, each of said sleeve sections having a slot thereinforreceivingtheshoulder of the 'arm, said shoulder and slotcombinedlydocking said sleeve'to said arm,,said recurve manuallycompressible "to remove said sh'oulderfrom said slot'to release saidcontacting means, a plurality'of arcuate rows of contacts, each of saidrows tactually adjacent one of said contacting means, each of said rowsof contacts'havinga solid conducting semi-circularring radially inwardthereto, each of said contactingmeans capable of completing a circuitfrom the ringto individual contacts of the adjacent row,=each' orsaid-contacting means advancing to successive contacts within arow oneach of said reciprocating cycles of said driving means.

9. In a stepping switch comprising a wiper assembly and stepping meansfor operating saidassembly in successive stepping operations, saidassembly comprising a main bodyportion, wiper arms and wiper tipsdetachably mounted on said wiper arms, said-wiper arms each having aportion thereof molded in said body; portion and a free endextendinglongitudinally therefrom, said wiper arms each having atdiagonal slot inthe .free ends thereof forming acompressible hook, a protuberance onsaid hook, said wipertips each comprising a pair of wiper fingerson-one-endand a channelportion at the other end slidably positioned on awiper arm, and a slot in* said channel portion of each said wiper tipcooperatingwith aprotuberance on one of said wiper arms for detachablylockingawiper tip to a wiper anm, said slot in-saidhook permittingmanual depression of said protuberance and compression of said hook toenable manual removal of a wiper tip from a wiper arm.

10. In a rotary switclna contact bank having a plurality of levels ofequi-spac'ed contacts, each of said levels having an insulator on whichsaid contacts are arrayed in an arcuate path, a wiper individual to eachof said levels movable across the level to tactually engage successivecontacts, means integral to each of said levels for maintaining saidwiper movement substantially' in a plane parallel to the level, saidmaintaining means comprising a series of raised elliptical prisms alongthe wiper movement path, one: of said prisms located betweeneach of saidcontacts, the minor diameter of said elliptic prisms coveringsubstantially the transverse spacing between said contacts in themovement path, said prisms further providing insulation betweensuccessive contacts of a level.

11. In a rotary stepping switch, a plurality of arcuate levels ofstationary contacts, a wiper assembly having a central core, means forrotating said assembly in a step by step manner, a motive wiper settactually adjacent each of said levels, each of said motive Wipersetshaving a sleeve extremity, a series of protruding arms extending fromthe central core of said wiper assembly, means on each of saidprotruding arms for mating with one of said sleeve extremities to firmlyhold the motive wiperset in position to tactually engage stationarycontacts of the adjacent level, each of said arm means individuallycompressible manually to release the sleeve and thereby release thewiperset held thereon.

12. In a rotary stepping switch, a plurality of levels of axiallyaligned contacts, the contacts of each level spaced to comprise asemi-circular sector, each of said levels having a solid annularconducting band within the 10 sector of and coplanar to the contacts ofthe levels, conductive means for completing a circuit from a contact ona particular level to the conducting band of that level, said conductivemeans comprising a first contactor adjacent the contact, a secondcontactor adjacent the conducting band and a conductive paththerebetween, means external to said completed circuit for rotating saidconductive means to cause said second contactor to sequentially traversesuccessive contacts on that level, said rotating means including a Wiperblock having a plurality of arms extending outwardly in one directionfrom said block, each of said arms having mounted thereto a wiperassembly including said conductive circuit completing means.

References Cited in the file of this patent UNITED STATES PATENTS1,388,541 Woodbury Aug. 23, 1921 2,559,075 Horlacher July 3, 19512,600,938 Thierfelder June 17, 1952 2,699,468 Unk Jan. 11, 1955

